THERMAL ANALYSIS OF RETURN LINE OF A HYDRAULIC SYSTEM

THERMAL ANALYSISOF RETURN LINE OF AHYDRAULIC SYSTEM

By:- Ryan D'Souza Nitish Kulkarni Nitish Kale Project Guide :- Mahesh Mulik Prof S. R.Kandharkar

Problem StatementThe Hydraulic Steering Systems encounter a problem of Return Line Failure due to changes in the hydraulic fluid properties with changes in operating conditions. The return line failure can cause entire failure of the hydraulic steering system and threatens the safety of the driver and passengers.

Project ObjectiveAnalyze the causes of the return line failure in steering systems. Analyze the changes in the various properties of the hydraulic fluid in the system and the parameters affecting it.Suggest methods to prevent return line failure.

Real-Life CasesA large-scale recall relating to the failure of power steering was covered extensively in the news. In late May 2014, 1.4 million vehicles were recalled by the Ford Motor Company. According to a May 29, 2014 article in USA Today, at least 5 accidents and 6 injuries have been linked to the Escape and Mariner defect, and 15 accidents and 2 minor injuries have been linked to the Explorer problem.

Warning to 223,000 Mini drivers after cars suffer sudden failure in power steering - Daily Mail Reporter 18 February 2009 Angry drivers are urging Mini to recall almost a quarter of a million cars following a spate of sudden power steering failures. Many motorists have had frightening experiences and near-miss crashes after the system abruptly cut out, making controlling their vehicles extremely difficult. The fault is believed to be a problem in 223,000 Minis bought between 2001 and 2007. Mini's power steering pumps are failing so early in the car's life and is concerned by the risks the failure can cause.

Hydraulic Power Steering System Use mass transfer to achieve desired output with minimum effort.Greatly reduces the driving effort & made driving safer and comfortable.The power steering system consists of three components: -power steering pump -power fluid reservoir -power steering rack and pinion gear

Steering System

The Main Components Of Hydraulic Steering System

Pump Steering Unit Steering Column Actuator Filter Reservoirs Hoses and Fittings

Advantages of Power SteeringPowerFlexibilityOperator comfortControlWeightSmoothness

SETUP SPECIFICATIONSPump Max. Pressure - 140 bar at 2000 rpm Max. Flow Rate 8 lpm at 2000 rpmActuator 1. Bore 90 mm2. Stroke 450 mm 3. Volume 2862776.3 mm3 = 0.002863 m3Reservoir Capacity 1.5 litersSteering Fluid Fiat Palio Steering Fluid 1. Specific Gravity 0.8742. Flash Point 185oC3. Pour Point - -40oC4. Viscosity Index 1555. Viscosity at 40oC 37.3 cSt 100oC 7.1 cSt

HYDRAULIC SYSTEMS AND FLUIDSUsed in a variety of applications from car brake to heavy agricultural and construction and mining equipment.Hydraulic fluids are integral part of hydraulic systems.Modern hydraulic systems use petroleum based oils with additives to inhibit foaming and corrosion.Fluids have primary function of transferring potential and kinetic energy.

Types Hydraulic FluidsTypes of Hydraulic fluids:Petroleum Based FluidsSynthetic Based FluidsWater in oil Based FluidsHigh Water Based Fluids(HWBF)/High WaterContend Fluids(HWCF)Fire Resistant Fluids

Properties Of FluidsViscosityViscosity Index(VI)Chemical StabilityCompressibility/Bulk ModulusFoaming TendencyDensityGood Heat Dissipation

Test ProcedureAcquirement of required components (Steering system of Fiat Palio)Fabricating the stand for the system to rest and work without difficulties or collision Purchased the motor to run the pump , the belt required to do the same and finally the standard oil.Fitting RTDs in the inlet and outlet of return line .Simultaneously performing thermal analysis on software to simulate temperature patterns.Test run the system to find the leakages and rectify them making the system leak proof.Use of NI LabView for taking the readings .Taking the various readings by changing the various parameters(Oil, No Load Steering & steering in loaded condition)

ContinuedTabulation of the readings for further calculations using Microsoft Excel. Generating the graphs and result table.Analysing the found results.

CalculationsThe return line is the major area of concern. The heat transfer from the steering fluid to the surroundings is divided into three main modes- 1. Heat transfer by convection between the steering fluid and inner walls of return line. 2. Heat transfer by conduction along pipe thickness from inner wall to outer wall of pipe. 3. Heat transfer by convection from outer wall of pipe to surroundings

Mathematical Model of the system also called as electric analogy

To find average change in the temperature over the whole return line we have opted for finding the Logarithmic Mean Temperature Difference (LMTD) of the same. Here the temperature Tin is the temperature at the inlet of the return line. The temperature Tout is the temperature at the outlet of the return line. Tatm is the Ambient or Surrounding temperature, taken as 26 C. TIA is the difference between Inlet and Ambient Temperature. TOA is the difference between Outlet and Ambient Temperature. Difference T = TIA - TOA

Logarithmic Mean Temperature Difference (LMTD) is =/() Total heat transferred in the system is Q Q=U*A*LMTD U is Overall Heat Transfer Rate A is the Area of the pipeThe readings were taken in interval of 2 minutes and directly exported to Microsoft Excel. These readings where converted into intervals of 5 minutes for tabulation on results. The readings are from time 0-60 minutes. All the required calculations was done and formulated into a table. This final data was used for analysis and graph plotting.

ForecastAs per our study the following should be the results: With steering the temperature rise should be more.With addition of steering load ,the temperature rise should be more.The oil with better properties should have less temperature rise.We have verified the above parameters in our test results.

Results Achieved Comparison between the condition of steering and without steering

Comparison between the condition of with and without load on the system

Comparison between the use of different oilsFirst oil has the viscosity of 7.2 mm2/sec & VI is 182,Second oil has the viscosity of 7 mm2/sec & VI is 150.This justifies our results.

Thermal Analysis of Return LineTransient thermal analysis done on return line, as time interval increases, temperature at inlet to return line increases. According to it temperature distribution pattern varies. Temperature at inlet to return line goes on increasing as the time interval increases. The conditions had been achieved at no load and at room temperatures which differs from actual working conditions as in temperature due to engine as well as other auxiliaries which radiate heat near steering return lines, which will cause further increase in temperature of the fluid.

Temp Range (30-60oC), Time Interval : 120 Minutes

Temp Range (30-40oC), Time Interval : 40 Minutes

Future Scope

Use of alternative material for making the hoses and testing their effect on the system.Additives and enhancement of the oil for better properties and their testing.Effects of increasing the length of return line & employing metallic finned pipes on the system.Change in heat dissipation rate after employing air coolers.

ConclusionWe found that temperature rise was one of the main reason of failure of system & were selected for further studies. Tests were conducted & from these tests we found relationship existing between the parameter and the system failure(Heating of oil) Incorrect oil selection with inappropriate properties leads to heating of system. Reduction in the oil volume also heats up the system. Increase in steering weight also leads to heating up of the oil. Thus, we can conclude that use of metal hose, increasing length of the return line, applying the principle of critical radius of insulation, and use of steering fluid with better properties are the possible solutions to the problem of Return Line Failure in hydraulic steering systems. The suitable measure can be employed considering constraints on the system.

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