A Study on the Design of Back Pressure for Automotive Scroll Compressor

구인회,이건호 대한설비공학회 2009 International Journal Of Air-Conditioning and Refr Vol.17 No.1

The optimum design of back pressure chamber is one of the most important factors in designing scroll compressors because it has a great influence on the efficiency and other design parameters. The design process can be divided into 2 parts. One is obtaining the optimum pressure of the chamber and keeping it in constant value. The other is finding out the minimum inflow rate of medium with which back pressure chamber is filled. In this study we are focused on the first step. At first we added a simple structure that can change back pressure without reassembling compressor. It makes possible to obtaining optimum back pressure. Then we designed an equipment that the back pressure control valve assembly could be independently tested with. Spring was redesigned to decrease stiffness variation. Also sealing mechanism of back pressure control valve was improved to more effective way. As a result, it was verified that in a real mode test back pressure variation could be retained in 2.3 % with discharge pressure and operating frequency varied. In addition the integrated structure of back pressure control valve is expected to contribute to effective manufacturing process. The optimum design of back pressure chamber is one of the most important factors in designing scroll compressors because it has a great influence on the efficiency and other design parameters. The design process can be divided into 2 parts. One is obtaining the optimum pressure of the chamber and keeping it in constant value. The other is finding out the minimum inflow rate of medium with which back pressure chamber is filled. In this study we are focused on the first step. At first we added a simple structure that can change back pressure without reassembling compressor. It makes possible to obtaining optimum back pressure. Then we designed an equipment that the back pressure control valve assembly could be independently tested with. Spring was redesigned to decrease stiffness variation. Also sealing mechanism of back pressure control valve was improved to more effective way. As a result, it was verified that in a real mode test back pressure variation could be retained in 2.3 % with discharge pressure and operating frequency varied. In addition the integrated structure of back pressure control valve is expected to contribute to effective manufacturing process.

가로막 스트레칭 기법에 의한 허리통증 환자의 최대들숨압력과 최대날숨압력, 허리 가동성 변화

공인영 대한고유수용성신경근촉진법학회 2023 PNF and Movement Vol.21 No.2

Purpose: This study aimed to confirm the effectiveness of the diaphragm stretching technique as a treatment method for low back pain by evaluating maximum inspiratory pressure, maximum expiratory pressure, and changes in back mobility in patients with low back pain. Methods: Thirty-four patients with low back pain were randomly divided into two groups: an experimental group and a control group. The diaphragm stretching technique was conducted in the experimental group, and the placebo intervention was conducted in the control group. The diaphragm stretching technique was conducted once, maintaining tension for 7 min. The placebo intervention was conducted in the same position as the diaphragm stretching technique, but with only light contact maintained without pressure. Maximum inspiratory pressure, maximum expiratory pressure, and back mobility were measured before and after the intervention, and the changes were compared and analyzed. A paired sample t-test was used to compare measurements within the group before and after the intervention. An independent t-test was used to compare the experimental and control groups. Statistical significance (α) was set at 0.05. Results: In the experimental group, maximum inspiratory pressure, maximum expiratory pressure, and back mobility increased significantly after the intervention (p < 0.05). However, there was no significant difference in the changes in all areas of the control (p > 0.05). As a result of comparative analysis of changes before and after the intervention, there were significant differences in maximum inspiratory pressure, maximum expiratory pressure, and back mobility only in the experimental group (p < 0.05). Conclusion: The diaphragm stretching technique improved maximum inspiratory pressure, maximum expiratory pressure, and back mobility compared to the placebo intervention. Therefore, the diaphragm stretching technique can be recommended as a physical therapy intervention to improve pain in patients with LBP.

스크롤 압축기의 배압조절 밸브 설계에 관한 연구

전성현,김영주,전병일,서삼원,임정택,김현진 대한설비공학회 2024 설비공학 논문집 Vol.36 No.4

축 방향 순응기구로서 배압 방식을 사용하는 스크롤 압축기에서 적정 배압 형성을 위한 배압조절 밸브에 대한 설계 연구에서, (1) 토출압과 흡입압의 변화에 따라 최적의 배압 수준도 함께 변화하지만, 최적 배압과 상당히 가까운 수준의 배압을 일정 값의 배압 계수를 통해 얻을 수 있다. (2) 원하는 배압 계수는 설계된 배압조절밸브의 피스톤 면적비 설정을 통해 얻을 수 있다. (3) 운전 압력 조건이 변화할 때, 설정된 배압 계수를 제공해 주는 배압조절밸브를 통해 원하는 배압을 얻을 수 있는지를 밸브 성능 모델링과 수치 해석을 통해 확인하였다. (4) 피스톤과 실린더 사이 간극이 2.5 ㎛인 경우, 간극 누설로 인해 배압 계산 결과치는 설정 배압보다 약 1% 높게 얻어진다. 이는 실용적으로는 전혀 문제가 없는 수준이다. (5) 밸브의 응답성은 운전 압력의 변화 폭에 따라 달라지겠지만, 목표치에 95% 이상으로 접근하는 데는 대략적으로 0.02sec~0.05sec 이내에서 이루어진다. (6) 밸브 내부 누설 손실은 압축기 토출 유량의 약 0.1% 수준으로, 이는 기존의 배압 방식에서 일어나는 1% 수준의 손실보다는 상당히 작은 수준이다. 따라서 이 밸브는 특별히 CO2와 같은 고압 냉매를 사용하는 냉동 시스템에 더욱 유용할 것이다. This paper discusses the design of a pressure control valve that generates an appropriate back pressure in a back pressure chamber of a scroll compressor. Its performance is verified through performance analysis. The back pressure coefficient, which is defined as the ratio of difference between discharge pressure and back pressure to difference between back pressure and suction pressure, can be created using the piston area ratio of the designed pressure control valve. By selecting an appropriate value of the back-pressure coefficient obtained in this manner, a back pressure that closely approximates the optimal back pressure, which varies depending on the operating conditions across a wide range of operating pressure ratios, can be achieved. Additionally, leakage loss in this valve is significantly smaller than that in conventional back-pressure types that use a back pressure hole, making it particularly suitable for CO2 scroll compressors.

A Study on the Design of Back Pressure for Automotive Scroll Compressor

Koo, In-Hwe,Lee, Geon-Ho The Society of Air-Conditioning and Refrigerating 2009 International Journal Of Air-Conditioning and Refr Vol.17 No.1

The optimum design of back pressure chamber is one of the most important factors in designing scroll compressors because it has a great influence on the efficiency and other design parameters. The design process can be divided into 2 parts. One is obtaining the optimum pressure of the chamber and keeping it in constant value. The other is finding out the minimum inflow rate of medium with which back pressure chamber is filled. In this study we are focused on the first step. At first we added a simple structure that can change back pressure without reassembling compressor. It makes possible to obtaining optimum back pressure. Then we designed an equipment that the back pressure control valve assembly could be independently tested with. Spring was redesigned to decrease stiffness variation. Also sealing mechanism of back pressure control valve was improved to more effective way. As a result, it was verified that in a real mode test back pressure variation could be retained in 2.3% with discharge pressure and operating frequency varied. In addition the integrated structure of back pressure control valve is expected to contribute to effective manufacturing process.

Experimental and computational study on the dynamic interaction between load variation and back pressure control in a polymer electrolyte membrane fuel cell for automotive application

Kim, D.K.,Koh, J.S.,Kim, M.S.,Song, H.H. Pergamon Press ; Elsevier Science Ltd 2015 International journal of hydrogen energy Vol.40 No.36

Experimental and computational study on the operating characteristics of the fuel cell with changing back pressure at the cathode and anode outlets was performed for both steady and transient operations. In the experiments, the back pressure was controlled by a pressure regulator in the fuel cell outlet, and the effects of the operating pressure under various load conditions were observed in steady-state operations. The transient responses of the fuel cell to the load changes in different operating pressures were also examined. Additionally, in order to fully understand the effects of the major parameters in various operating pressures on the fuel cell performance, a dynamic simulation model of the cell stack was developed. The performance analysis revealed that a higher voltage was produced by the cell when a high pressure was maintained because the high pressure facilitated high concentration of the reactant gas near the membrane. The mass flow rate of the liquid water also increased with increasing pressure in a given humidity, which helped to maintain higher voltage than otherwise. However, the overshoot and undershoot of the output voltage during load transition also increased with increasing back pressure, primarily because of the difference between the rates of gas supply to the membrane and gas consumption near the membrane. Whereas the consumption of the gas near the membrane was rapid, the fresh reactant gas required some time to reach the membrane. The inherent time lag resulted in undershoot and overshoot with changing load. It was observed that the remaining liquid water was also an important factor which affected the level of undershoot or overshoot during the load change. Finally, an operating strategy using a back-pressure regulator was suggested and applied in a transient operation of irregular multi-step load variation. The back pressure should be decreased before the load change and restored back to the pre-set level for the steady-operation. The former was shown to reduce the size of undershoot or overshoot during transition, and the latter could lead to the efficient operation by reducing parasitic losses in the fuel cell system.

만성 허리통증에 대한 Kinesio taping 적용이 허리압통과 균형능력에 미치는 영향

유창현,김윤환,김태원 대한정형도수물리치료학회 2022 대한정형도수물리치료학회지 Vol.28 No.2

Background: This study investigated the effects of kinesio taping application on lower back pressure pain and balance ability among university students with chronic lower back pain. Methods: A total of thirty university students between 20 to 30 years of age with chronic lower back pain were divided randomly into two groups, the control and the experimental group. In the control group (n=15), placebo taping was applied to the lumbar region. In the experimental group (n=15), kinesio taping was applied to the erector spine muscles of the lower back. The groups were assessed for lower back pressure pain and balance ability, before and after the taping application. Pain was measured by the pain pressure threshold (PPT), and balance was measured using the good balance system (GBS). Results: There were significant improvements in both the PPT and GBS of the kinesio taping group compared to pre-treatment values (p<.05), while the placebo taping group showed no significant change (p>.05). In addition, the kinesio taping group had a statistically significant difference in PPT and GBS compared to the placebo taping group (p<.05). Conclusion: The kinesio taping application is more effective than the placebo taping application in the improvement of lower back pressure pain and balance ability among university students with chronic lower back pain.

센서네트워크 수명 연장을 위한 에너지 임계값 기반 다단계 Back-Pressure 알고리즘

정대인(Daein Jeong) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.12B

본 논문에서는 센서네트워크의 수명 연장을 위해 에너지 인지 기반의 경로 제어 방안인 TBP(Threshold based Back-Pressure) 알고리즘을 제안하였다. 센서네트워크 수명 연장을 위해서는 에너지의 고른 소비가 필수적이므로, 라우팅 영역 전체에 걸친 고른 트래픽 분배를 설계목표로 갖는다. TBP 알고리즘은 지역적 트래픽 분배와 라우팅 영역 전체에서의 트래픽 분배를 모두 수행한다. 임계값과 back-pressure 신호가 이 두 가지 스케일의 트래픽 분배 수행을 위해 정의되었다. TBP 알고리즘은 라우팅 영역에 속한 다중경로의 최적 활용을 목적으로 하지만 이를 위해 사용하는 임계값과 back-pressure 신호는 한 홉 범위의 지역적 정보로 정의함으로써 망 규모에 제한받지 않는 확장성을 확보하였다. TBP 알고리즘이 에너지 소비를 분산시키는 효과, 즉 네트워크 수명을 연장하는 효과를 가지고 있음을 다양한 실험을 통하여 확인하였다. 또한, TBP 알고리즘은 엄격한 경로 제어를 기반으로 설계되었음에도 지연 및 전송률 지표에서 개선된 결과를 보였다. 에너지 인지 기반의 경로 제어가 트래픽 혼잡 제어의 효과를 부분적으로 갖고 있음을 보여주는 결과이다. This paper proposes an energy-aware path management scheme, so-called the TBP(Threshold based Back-Pressure) algorithm, which is designed for lifetime extension of the energy-constrained wireless sensor networks. With the goal of fair energy consumptions, we extensively utilize the available paths between the source and the sink nodes. The traffic distribution feature of the TBP algorithm operates in two scales; the local and the whole routing area. The threshold and the back-pressure signal are introduced for implementing those operations. It is noticeable that the TBP algorithm maintains the scalability by defining both the threshold and the back-pressure signal to have their meanings locally confined to one hop only. Throughout several experiments, we observe that the TBP algorithm enhances the network-wide energy distribution. which implies the extension of the network lifetime. Additionally, both the delay and the throughput outcomes show remarkable improvements. This shows that the energy-aware path control scheme holds the effects of the congestion control.

센서네트워크 수명 연장을 위한 에너지 임계값 기반 다단계 Back-Pressure 알고리즘

정대인 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.12

This paper proposes an energy-aware path management scheme, so-called the TBP(Threshold based Back-Pressure) algorithm, which is designed for lifetime extension of the energy-constrained wireless sensor networks. With the goal of fair energy consumptions, we extensively utilize the available paths between the source and the sink nodes. The traffic distribution feature of the TBP algorithm operates in two scales; the local and the whole routing area. The threshold and the back-pressure signal are introduced for implementing those operations. It is noticeable that the TBP algorithm maintains the scalability by defining both the threshold and the back-pressure signal to have their meanings locally confined to one hop only. Throughout several experiments, we observe that the TBP algorithm enhances the network-wide energy distribution. which implies the extension of the network lifetime. Additionally, both the delay and the throughput outcomes show remarkable improvements. This shows that the energy-aware path control scheme holds the effects of the congestion control. 본 논문에서는 센서네트워크의 수명 연장을 위해 에너지 인지 기반의 경로 제어 방안인 TBP(Threshold based Back-Pressure) 알고리즘을 제안하였다. 소스 노드로부터 싱크 노드로의 라우팅 영역 전체에 걸친 고른 트래픽 분배를 설계목표로 갖는다. TBP 알고리즘은 두 가지 스케일의 적용 영역을 갖는다. 지역적 트래픽 분배와 라우팅 영역 전체에서의 트래픽 분배이다. 지역적 분배는 이웃 노드들의 에너지 소비를 균등하게 유지하는 것이 목표이며, 라우팅 영역 전체를 활용하는 트래픽 분배는 라우팅 영역의 정점에 있는 소스 노드에서 모든 가용 경로들의 상태 정보를 참조하여 수행된다. TBP 알고리즘은 라우팅 영역에 속한 다중경로의 최적 활용을 목적으로 하지만 한 홉 범위의 지역적 정보만 사용함으로써 망 규모에 제한받지 않는 확장성을 확보하였다. TBP 알고리즘이 기존의 경로 기반 라우팅에 비하여 에너지 소비를 더욱 분산시키는 효과를 가지고 있음을 다양한 실험을 통하여 확인하였다. 또한, TBP 알고리즘은 엄격한 경로 제어를 기반으로 설계되었음에도 지연 및 전송률 지표에서 개선된 결과를 보였다.

The Correlation between Plantar Pressure and Low Back Pain and the Validity of Digital Foot Scanner

Hye Rin Cho,Han Suk Jung,Joo Hyun Ham 한서대학교 보완대체의학연구소 2012 Research Journal of Complementary and Alternative Vol.- No.3

The purposes of this study were to measure the index values of plantar foot pressure applied on both legs in standing position and to explore if there was correlation with low back pain, and further to examine the reliability of digital feet scanning devices. A total 125 college students(50 male students and 75 female students, aged from 20 to 29) participated this study. The foot plantar pressures were measured by AssociateⓇ Platinum V7+ Digital foot scanner. The reliability of AssociateⓇ Platinum V7+ Digital foot scanner was measured by two inspectors. Index values of plantar foot pressure measured at standing position were higher in the low back pain group then the normal population. Hereupon, it has been confirmed that back ache influenced on the plantar foot pressure. There was also a correlation between low back pain and foot pressure(r = 0.93, p < 0.01). There was also correlation between foot pressure and pain in standing position(r = 0.47, p < 0.01). In addition, according to the result of reliability on the AssociateⓇ Platinum V7+ Digital foot scanner, measured SEM was 3.22 on both groups along with MAD of 1.98±0.14 on each group as well. In addition, two groups had the same ICC3,1 as 0.75. In addition, it has been identified that there was a high reliability on the AssociateⓇ Platinum V7+Digital foot scanner by examining variables other than ICC3,1. This study showed a higher plantar in standing position under imbalanced condition. Therefore, it suggests maintaining a proper posture and precaution with exercise through education in a daily life. In addition, the results and methodology of this study could be served as a criteria used for measuring and evaluating postural imbalance of college students.

터보제트 복합추진시스템 흡입구의 배압 영역별 내부유로 유동박리 및 블리드 유량 변화 분석

김영진(Y.J. Young),한송이(S.E. Han),박수형(S.H. Park) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3

Inlet performance with the back pressure in the TBCC(Turbine-Based Combined Cycle) is analyzed in order to study a stable start of the turbojet engine. A reliable back-pressure boundary condition using total pressure extrapolation method is proposed to investigate the inlet performance and to obtain the turbojet compressor effect in high accuracy. Numerical results show that the location of flow separation of subsonic diffuser can be decided by the subsonic diffuser angle and the bleed effect. In low back-pressure, the total pressure recovery of the turbojet is very low because the terminal shock has relatively strong strength. In high back-pressure, the mass capture ratio is low because of the large amount of the bleed flow rate. Considering the stable flight of TBCC, a range of back pressure may exist even in the critical condition depending on the performance of the engine itself.