Decreasing Compression Ratio Research Articles

Experimental Investigation on a Vapor Injection Heat Pump System with a Single-Stage Compressor

In this study, a heat pump of 10 kW with vapor injection using refrigerant of R410A was developed. A vapor injection pipe connecting a gas–liquid separator at the outlet of the main expansion valve and the suction of a single-stage rotary compressor was designed. The heating performance of this vapor injection heat pump was investigated and analyzed at different compressor frequencies and primary temperatures. The experimental results show that for the heat pump without vapor injection, the heating capacity increased linearly with the compressor frequency, while the heating coefficient of performance (COP) decreased linearly with the compressor frequency for each tested primary temperature. The developed vapor injection technique is able to increase the heat pump system’s heating capacity and heating COP when the injection ratio R falls into the range 0.16–0.17. The refrigerant mass flow rate can be increased in the vapor injection heat pump cycle due to the decreased specific volume of the suction refrigerant. The power consumption of vapor injection heat pump cycle almost remains the same with that of the conventional heat pump cycle because of the increased refrigerant mass flow rate and the decreased compression ratio. Finally, it was found that the developed vapor injection cycle is preferable to decreasing the compressor’s discharge temperature.

Assessment of ultra-lean burn characteristics for a stratified-charge direct-injection spark-ignition methanol engine under different high compression ratios

Lean burn is one of the most important characteristics of a stratified-charge direct-injection spark-ignition engine. In this study, a non-uniform 10-hole × 0.30 mm spray-line distribution nozzle was chosen to achieve stratified-charge of the methanol/air mixture. The mixture formation, combustion, and emissions characteristics of a stratified-charge direct-injection spark-ignition methanol engine under five global equivalence ratios and three high-compression ratios were simulated to assess its ultra-lean burn characteristics. The results showed that the equivalence ratio of the stratified-charge direct-injection spark-ignition methanol engine for stable combustion at high compression ratio was as low as 0.20. The ignition delay and combustion duration decreased as the compression ratio increased at high equivalence ratio, and vice versa at low equivalence ratio. The stratified-charge direct-injection spark-ignition methanol engine greatly reduced nitric oxide emissions under ultra-lean combustion. The unburned methanol, carbon monoxide, and soot emissions increased slowly as equivalence ratio decreased at all compression ratios and equivalence ratio >0.25. The indicated thermal efficiency decreased with decreasing compression ratio at high equivalence ratio, and vice versa at low equivalence ratio. For an equivalence ratio of 0.67, the indicated thermal efficiency at compression ratio of 14 was approximately 14.9% lower than at compression ratio of 16. However, for an equivalence ratio of 0.20, the indicated thermal efficiency at compression ratio of 14 was approximately 13.5% higher than at compression ratio of 16. The compression ratio of 14 was more favorable for the stratified-charge direct-injection spark-ignition methanol engine to achieve ultra-lean burn and find practical application.

Performance and Brake Specific Fuel Cost of Constant Speed Diesel Engine for Acetylene As Alternative Fuel

Historical growth for development of power to fulfil the demands, together provides a challenge for depletion of fossil fuels. The internal combustion engines have a major share used to develop power. To fulfil the increasing demands, many researchers worked on diesel engine with biodiesel blends derived from edible and non-edible oils as an alternative fuel. Some researcher’s experimented gaseous fuels along with diesel also in which diesel will be primary fuel and gaseous fuels like acetylene will be secondary fuel. Increased rates of pollutants again required more focus in modification of engine sub-assemblies. The present study carried out to find the cost effectiveness while the constant speed diesel engine supplied 2 liter per minute flow rate of acetylene at different compression ratios. It realized that the brake specific fuel consumption and required cost to operate the engine, in case of duel fuel mode operation will be less for the compression ratio of 17. It was also noted that for idling or low load the operation of engine will be costly with duel fuel mode of operation and for maximum load the cost of operation will be barely same as the operation on only diesel. The results from performance analysis states that in duel fuel mode of operation by decreasing compression ratio to 17, no change in power out with decreased sound pressure. Also from emission analysis decreased CO2, HC emission found than only diesel operation.

Performance analysis of thermal vapor compression integrated with reverse osmosis desalination system

Based on the thermal and membrane desalination technology, this study presents an analysis of an integrated single stage TVC-RO system. The hybrid system produces fresh water with an adjustable salinity in parallel operation. A steam ejector and a pressure exchanger are applied as the energy recovery devices. For comparison, a coupling system without energy recovery process is also modeled in the steady-state condition. System performance is evaluated by specific energy consumption and production ratio. The effects of several design parameters on system performance are investigated including boiling temperature, compression ratio, motive steam pressure, and target recovery rate. Results of the analysis indicate that the product salinity is adjustable in the TVC-RO system, and the system performance is largely dominated by system configurations and design parameters. To improve the system performance, the use of energy recovery device is necessary, and the membrane operation is recommended if the process is less demanding on product purity. A better performance can be obtained by increasing the target recovery rate of the RO membrane and decreasing compression ratio and motive steam pressure of the ejector. As the boiling temperature increases, one can expect that the production rate increases at a cost of a higher specific energy consumption.

Image compression scheme based on PCA for wireless multimedia sensor networks

In combination of the characteristic of the network architecture of wireless multimedia sensor networks (WMSNs), a distributed multi-node cooperative network (DMCN) model is designed by using the concept of in-network processing to improve their energy, memory and computational power. To balance the energy consumption of the network, according to roles division, camera nodes and common nodes are cooperated to accomplish the workload of image acquisition, compression and transmission. Camera nodes gather images and send blocking images to the common nodes in cluster. Common nodes adaptively compress the partitioned images by using a noise-tolerant distributed image compression (NDIC) algorithm based on principal component analysis (PCA) called NDIC-PCA algorithm and send the compressed data to the cluster head node. Then, the cluster head node sends the compressed image data to the station. Simulation results demonstrate that, DCNM can effectively balance the energy consumption of network and largely extend the network lifecycle. In addition, compared with previous algorithms, the proposed NDIC-PCA algorithm achieves higher peak signal to noise ratio without decreasing compression ratio.

Effect of compression ratio on performance and emissions of a stratified-charge DISI (direct injection spark ignition) methanol engine

Experiments were conducted on a single-cylinder, four-stroke, water cooled, stratified-charge DISI (direct injection spark ignition) methanol engine which was modified from a diesel engine. The effects of compression ratio on the torque, power, brake thermal efficiency and exhaust emissions of a DISI stratified-charge methanol engine were investigated and the all aforementioned parameters were compared with the diesel counterpart. The analysis of compression ratio on combustion behavior of methanol engine was performed. The torque and power of methanol engine decrease not more than 3.5% when the compression ratio decreases from 16 to 14. Its brake thermal efficiency increases at low load and decreases at high load with the compression ratio decreases. Decreasing compression ratio can decrease obviously its maximum pressure rise rate and improve the brake thermal efficiency at low load. As a result, decreasing compression ratio from 16 to 14, brake thermal efficiency of methanol engine increases by 18% at low load, and brake thermal efficiency decreases by 6% and maximum pressure rise rate decreases up to 60% at high load and maximum torque engine speed. Moreover, HC and NOX emissions of methanol engine increase with an increase in the compression ratio, and vice verse on CO emission.

A study of combustion and emissions characteristics of a compression ignition engine processes using a numerical tool

Experimental analysis of a diesel engine gives only the global picture of the in-cylinder processes, through averaged quantities. These averages are sometimes global averages or in some cases taken at each crank angle. To understand the in-cylinder processes better, the distribution of scalars becomes very important. In this paper, Converge, a CFD-tool was used to simulate the closed cycle in-cylinder process of a diesel engine to develop deeper insights into the effects of various injection parameters and compression ratio on engine performance and exhaust emissions. Results from Converge CFD-tool have been validated against the experimental data published in the literature. Effects of compression ratio, number of injector holes, spray angle, half cone angle and injection duration were studied using the validated model. Simulation results indicate that decreasing compression ratio resulted in a significant reduction in NO concentrations with a slight increment in specific fuel consumption (SFC). A narrow spray angle resulted in a considerable reduction of soot and SFC. Spray-to-spray interaction was increased with increasing number of nozzle holes. As a result, higher SFC, CO and soot were observed with increasing number of nozzle holes. Various in-cylinder contour plots showed that the injection with higher injection duration i.e. lower injection pressure produces relatively lower extent of fuel wall wetting and hence resulted in less intensity flames close to the piston head. Increasing the spray angle, number of holes and injection duration resulted in clear decline in exhaust NO concentration.

Aerodynamics Numerical Study on Vapor Flowing of the Oil Booster Pump

The pumping power of oil booster pump is the vapor jet stream that determined pump performance. The key importance is the study of vapor flowing characteristics, and also is the method of improvement pump structure and saving energy. The aerodynamics is adopted to study the oil vapor flowing characteristics. The study shows that it should adopted the higher oil boiler pressure in order to increase the density of the oil vapor, and so it can be benefit to pumping gas in 1Pa—10Pa. The nozzle divergence angle and divergence rate also should be increased in order to increase the oil vapor velocity and kinetic energy, and so increased the pumping rate on 0.1Pa. Increasing divergence angle and divergence rate of the first nozzle at constant compression ratio, the upper bottom of jet stream can be moved up, and the eject stream thickness was increased. In other word, increasing the compression ratio at constant eject stream thickness, the oulett pressure was increased. When the pump was operated at higher pressure, it should be decreased compression ratio of first stage. The main pump body was also designed to prominence chamber in order to increase the pumping rate.

Formation and Destruction of Vortices in a Motored Four-Stroke Piston-Cylinder Configuration

THE effects of the compression ratio, engine speed, boreto-stroke ratio, and valve seat angle on the turbulent flowfield within an axisymmetric piston-cylinder configuration have been studied by means of an implicit finite difference method which solves the conservation equations of mass, momentum, and energy, and two additional equations for the turbulent kinetic energy and its dissipation rate. The numerical results indicate that the turbulent intensity at topdead-center of the compression stroke is independent of the rpm and decreases with decreasing compression ratio. The turbulent intensity also increases when decreasing the bore-tostroke ratio. It has been found that the valve seat angle has the most important effect on the flowfield. A valve seat angle of 45 deg produces two vortical structures which break down and merge by the end of the compression stroke, and persist into the expansion stroke. For smaller valve seat angles there is no vortex breakdown and the vortical structures created during the intake stroke disappear by the end of the compression stroke. The importance of vortical structures on fuel mixing and turbulence levels within an internal combustion engine is also discussed. Contents The purpose of this paper is to report some numerical results concerning the effects of the compression ratio, boreto-stroke ratio, rpm, and valve seat angle on the formation and destruction of vortices, and turbulent levels within an axisymmetric piston-cylinder configuration equipped with a centrally located valve. The calculations reported here were performed with an implicit finite difference algorithm that solves the conservation equations of mass, axial and radial momentum components, and energy. Turbulence has been modeled by means of a two-equation model for the turbulent kinetic energy and its dissipation rate. The motion of the valve has been accounted for by means of the two-domain technique developed in Ref. 1. Calculations were performed at several engine speeds, i.e., rpm, and showed that as long as the valve seat angle is less than 45 deg (this angle is measured with respect to the engine cylinder centerline) the flowfield in the intake stroke is characterized by the formation of two vortical structures. One of these structures is located at the corner between the cylinder

Paper 7: The Turbo-Charged Diesel as a Road Transport Power Unit

The lowest possible cost of transport determines the choice of vehicle engine. Installation space, weight, and fuel consumption favour turbo-charged diesels which also have good smoke and noise characteristics. Much development work has been done at Volvo to increase reliability as regards the turbo-charger unit, cylinder head gaskets, valve wear, and bore scuffing. In this connection a decreased compression ratio is an important factor. However, cold starting and white smoke under part load must be solved in a way that does not decrease reliability.