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A Generic Testbody for Low-Frequency Aeroacoustic Buffeting Phenomena

BMW Group, Munich, Germany-Rafael Engelmann, Christoph Gabriel
Vienna University of Technology-Stefan Schoder, Manfred Kaltenbacher
  • Technical Paper
  • 2020-01-1515
To be published on 2020-06-03 by SAE International in United States
Raising demands towards lightweight design paired with a loss of originally predominant engine noise pose significant challenges for NVH engineers in the automotive industry. Wall thickness reductions particularly emphasize low frequency contributors due to decreasing panel stiffness. From an aeroacoustic point of view, low frequency buffeting ranks among the most frequently encountered issues. The phenomenon typically arises from rooftop or side-window buffeting, structural transmission of hydrodynamic wall pressure fluctuations or, as indicated in this work, through rear vent excitation. A convenient workflow to simulate structure-excited buffeting contains a strongly coupled vibro-acoustic model for structure and interior cavity excited by a spatial pressure distribution obtained from CFD. In the case of rear vent buffeting no validated workflow has been published yet. While approaches have been made to simulate the problem for a real-car geometry, such attempts suffer from tremendous computation costs, meshing effort and lack of flexibility. Additionally, low frequency structural behavior strongly depends on appropriate boundary conditions being subject to manufacturing and mounting tolerances. The goal of this work is to develop, simulate and experimentally…
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Simulation of Hybrid Packed Desiccant beds for De-humidification and Drying

Vellore Inst. of Technology, Vellore-Selvaraji Muthu, Sekarapandian N
  • Technical Paper
  • 2020-28-0019
To be published on 2020-04-30 by SAE International in United States
The conventional vapour compression refrigeration cycle based air dryers are used widely for the applications requiring pressure dew point temperature ranging between 2°C to 3°C. However, for the industrial and pneumatic applications, the required pressure dew points are as low as between -10°C to -75°C. This kind of low pressure dew points can be achieved by the adoption of adsorption based packed bed desiccant dryer technology. In this paper the numerical investigation of the performance of a packed bed desiccant dryer containing homogenous mixture of multiple desiccant types along the vertical axial direction using an in-house finite volume based CFD code is presented. The developed code has the capability to model the coupled heat and mass transfer taking place in a packed hybrid bed desiccant dryer during the adsorption and desorption phases. The numerical results obtained for the base model are validated against relevant experimental data for exit air temperature and moisture content available in the literature and found to have good agreement. Subsequently using the validated numerical model, the improvement in moisture removal capacity,…
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Dynamic behavior of in-cylinder pressure causing fatigue failure of reed valves

Subros Ltd.-Ankit Shukla, Paulson Parayil, Arun Kumar Goel, Kamal Sharma
  • Technical Paper
  • 2020-28-0031
To be published on 2020-04-30 by SAE International in United States
For years, researchers have presented numerous studies that consider interaction between working fluid and reed valve motion in displacement compressors. The computing capacities and available CFD and FEA simulation tools have allowed modeling of fully coupled interaction of fluids and moving structures. The present paper describes our experience and results from developing a simplified model of a multi-cylinder reciprocating piston compressor and estimation of pressure surge during sudden acceleration of such compressors. The results show that sudden speed change causes surge in pressures due to formation of pressure waves that reflect back and forth within cylinder. For the chosen geometry and operating conditions, the duration of such waves is much shorter (~ 0.2ms) as compared to longer response time of reed valves (1 ms) that are stiff and highly inelastic. These high pressure waves eventually exceed the fatigue limit of reed valves and cause failures. These pressure waves also influence the performance of reciprocating by causing noise and vibrations which eventually dissipate in to heat thereby lowering the COP of compressor. Simulation results compare well…
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CFD investigation of exhaust gas bypass on truck trolley heating

John Deere India Private, Ltd.-Nitin Dewangan
John Deere India Pvt Ltd-Megha anawat
  • Technical Paper
  • 2020-28-0006
To be published on 2020-04-30 by SAE International in United States
Most of the automobile and off-road vehicles leave the 100% exhaust gases to atmosphere. The temperature of the exhaust gas ranges from 200-350 deg C and the exit velocity of the gas is about 40-100 m/s based on the outlet pipe design. Dump trucks are used to transport mud, sticky waste garbage and sometime ice from one place to dump yard. The paper will describe the approach of partially use the exhaust gases for truck trolley by heating the trolley surfaces from the walls. CFD software is used to evaluate the exhaust system pressure drop and bypass exhaust flow rate requirements for effective heating on trolley wall. The simulation also helped to design the appropriate baffle position for optimum pressure drop and recirculation. Conjugate heat transfer CFD analysis is carried out to predict the flow behavior.
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MIMO Control of a Turbogenerator for Energy Recovery

Loughborough Univ.-Simon Petrovich, Kambiz Ebrahimi, Nikolaos Kalantzis, Antonios Pezouvanis
  • Technical Paper
  • 2020-01-0261
To be published on 2020-04-14 by SAE International in United States
Market trends for increased engine power and more electrical energy on the powergrid (3kW+), along University of Loughborough for fuel consumption improvements and emissions reduction, are driving requirements for component electrification, including turbochargers. GTDI engines waste significant exhaust enthalpy; even at moderate loads the WG (Wastegate) starts to open to regulate the turbine power. This action is required to reduce EBP (Exhaust Back Pressure). Another factor is catalyst protection, where the emissions device is placed downstream turbine. Lambda enrichment or overfuelling is used to perform this. However, the turbine has a temperature drop across it when used for energy recovery. Since catalyst performance is critical for emissions, the only reasonable location for an additional device is downstream of it. This is a challenge for any additional energy recovery, but a smaller turbine is a design requirement, optimised to operate at lower pressure ratios. A WAVE model of the 2.0L GTDI engine was adapted to include a TG (Turbogenerator) and TBV (Turbine Bypass Valve) with the TG in a mechanical turbocompounding configuration, calibrated with steady state…
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Minimizing Disturbance Detection Time in Hydraulic Systems

General Motors LLC-Paul Otanez, Ramadityanand Bhogadi
  • Technical Paper
  • 2020-01-0263
To be published on 2020-04-14 by SAE International in United States
In a hydraulic system, parameter variation, contamination, and/or operating conditions can lead to instabilities in the pressure response. The resultant erratic pressure profile produces reduced performance that can lead to hardware damage. Specifically, in a transmission control system, the inability to track pressure commands can result in various types of slip and disturbances to the driveline. Therefore, it is advantageous to identify such pressure events and take remedial actions. The challenge is to detect the condition in the least amount of time while minimizing false alarms. In this study, cross and auto-correlation techniques are evaluated for the detection of pressure disturbances. The performance of the detectors is measured in terms of speed of detection and robustness to: 1) measurement noise, and 2) disturbance parameter uncertainty (frequency and amplitude). The implications in terms of computations and memory utilization of implementing the detectors in real-time embedded systems are also discussed. Both simulation and hardware examples are presented. The hardware experiment is performed in a hydraulic system with low damping composed of a solenoid and a regulator valve…
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Use of Partial Recirculation to Limit Build-Up of Cabin Carbon Dioxide Concentrations to Safe Limits per ASHRAE Standard-62

Calsonic Kansei North America Inc.-Gursaran Mathur
  • Technical Paper
  • 2020-01-1245
To be published on 2020-04-14 by SAE International in United States
Carbon dioxide exhaled by occupants remains within the cabin during operation of HVAC unit in recirculation mode. The CO2 inhaled by the occupants goes into their blood stream that negatively affects occupant’s health. ASHRAE Standard-62 (1999) specifies the safe levels of carbon dioxide in conditioned space for humans. The CO2 concentration limit per ASHRAE is 700 ppm over ambient conditions on a continuous basis. Based on the test data, at worst case scenario (idle condition where body leakage will be a minimal) results in CO2 concentrations of 1601, 2846, 4845 and 6587 ppm respective for 1 to 4 occupants in 30 minutes.Author has also conducted test by imposing ASHRAE standard-62. A controller was programmed for operating the blower unit’s intake door to go from recirculation to OSA mode when the measured carbon dioxide ppm level goes above 1100 ppm. The door stays in OSA mode until the cabin carbon dioxide falls to approximately 500ppm. By imposing these limits, the blower unit’s intake door cycles between 3 minutes to 6.5 minutes with four to one occupants…
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Emissions Benefits of Group Hole Nozzle Injectors under Conventional Diesel Combustion Conditions

Marquette University-Adam Dempsey
University of Wisconsin-Aravindh Babu, Daniel Staaden, Sage Kokjohn
  • Technical Paper
  • 2020-01-0302
To be published on 2020-04-14 by SAE International in United States
This work explores the effectiveness of common rail fuel injectors equipped with Grouped Hole Nozzles (GHNs) in aiding the mixing process and reducing particulate matter (PM) emissions of Conventional Diesel Combustion (CDC) engines, while maintaining manageable Oxides of Nitrogen (NOx) levels. Parallel (pGHN), converging (cGHN) and diverging (dGHN) - hole GHNs were studied and the results were compared to a conventional, single hole nozzle (SHN) with the same flow area. The study was conducted on a single cylinder medium-duty engine to isolate the effects of the combustion from multi-cylinder effects and the conditions were chosen to be representative of a typical mid-load operating point for an on-road diesel engine. The effects of injection pressure and the Start of Injection (SOI) timing were explored and the tradeoffs between these boundary conditions are examined by using a response surface fitting technique, to identify an optimum operating condition. It is found that the GHNs offer a significant PM benefit along with a negligible NOx effect and that the cGHN and dGHN nozzles give the best PM performance at…
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Numerical investigations on strong knocking combustion under compression ignition conditions

State Key Lab of Engines-Jiaying Pan
Tianjin University-Lin Chen, Jianfu Zhao
  • Technical Paper
  • 2020-01-1137
To be published on 2020-04-14 by SAE International in United States
Homogeneous charge compression ignition (HCCI) combined with high compression ratio is an effective way to improve engines’ thermal efficiency. However, the severe thermodynamic conditions at high load may induce knocking combustion thus damage engine body. In this study, compression ignition knocking characteristics were parametrically investigated through RCM experiments and simulation analysis. First, the knocking characteristics were optically investigated. The experimental results show that there even exists detonation when the knock occurs thus the combustion chamber is damaged. Considering both safety and costs, the effects of different initial conditions were numerically investigated and the results show that knocking characteristics is more related to initial pressure other than initial temperature. The initial pressure have a great influence on peak pressure and knock intensity while initial temperature on knock onset. Further analysis shows that knock intensity is mainly related to the energy density of the in-cylinder mixture and energy density is higher under higher pressure conditions. Then the effects of different cylinder wall temperature on the local auto-ignition thus knocking characteristics were further discussed. The results show that…
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Instantaneous PLII and OH* Chemiluminescence Study on Wide Distillation Fuels, PODEn and Ethanol Blends in a Constant Volume Vessel

Birmingham University-Hongming Xu
CNPC Ji Chai Power Co., Ltd.-Dong Liu
  • Technical Paper
  • 2020-01-0340
To be published on 2020-04-14 by SAE International in United States
The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere. Comparing with WD, the soot amount of WDEP decreased for 55% and 27% at 870 K and 920 K. For the case of 920 K and 15.8% of ambient oxygen, the soot amount…