Reply With QuoteDo you do oil analysis?Originally Posted by PAT303
YarnMaster
Direct measurement of temperature in the combustion chamber is appealling, but easier said than done. I considered using thermocouples in place of the glow plugs, but it soon becomes apparent that a thermocouple would not be practical.
I don't have data for how combustion chamber temperature changes, but expect it to be somewhat related to the heat released during combustion and expansion as the piston travels down the cylinder. The 1st pic below shows the normalised heat release rate per degree of crankshaft rotation for a typical, normally aspirated diesel engine - the heat release rate was normalised by dividing by the product of total mass of fuel injected and the heating value of the fuel. The negative dip is due to fuel vapourisation and endothermic pre-flame reactions. When autoignition occurs, the heat release rate rises rapidly - the large spike is much smaller or non-existant with highly turbocharged engines.
One crankshaft revolution takes 0.03 seconds (30 msec) at 2000 rpm. To my way of thinking, to be meaningful we would need to measure the temperature at intervals less than 30 degrees, which is 2.5 msec at 2000 rpm.
Thermocouples use an effect know as Seebeck effect (after its discoverer Thomas Seebeck) whereby the junction between two metals generates a voltage which is a function of temperature. For example, the K type thermocouple, which uses Chromel (Nickel-Chromium) and Alumel (Nickel-Aluminium) as the 2 metals produces 12.2 mV at 300C.
When a step change to the temperature being measured occurs, there is a response time for the voltage to change. This response is specified as a time constant, defined as the time required for the voltage to reach 63.2% of the voltage corresponding to the new temperature being measured. The thermocouple requires five time constants for the voltage to approach 100% of that corresponding to the new temperature.
The conductivity and motion of what is being measured has a very large bearing on the response - air is a poor conductor compared to water, so the time constant in air is much greater. How/where the thermocouple is mounted also affects the response e.g. a thermocouple mounted to a manifold will take longer to respond to a change in temperature of gas because of the thermal properties of the manifold.
An exposed junction thermocouple provides fastest response. Smaller wire provides faster response, but the maximum temperature may be lower (accuracy/reliability is affected by diffusion of atmospheric particles and other impurities into the wire at high temperatures). When the thermocouple is protected by a sheath, the smaller the sheath diameter, the faster the response. Sheathed probes of the grounded junction type (thermocouple juction grounded to the sheath) provide better response. See 2nd pic below.
The 3rd and 4th pics below compare time constant to diameter of wire or sheath, for exposed junction and grounded junction type thermocouples, calculated for air at room temperature and atmospheric pressure moving with a velocity of 65 feet per second. For beaded-type and ungrounded junctions, multiply the time constant by 1.5.
Swaggie
Do you do oil analysis?
OldBushie
Why?. Pat
Swaggie
To see if there were any significant changes after LPG was installed. I assume you do oil analysis on your fleet at the mine?
This paper is badly written, but you get the idea...
There are several similar studies.Study on biogas premixed charge diesel dual fuelled engine
Phan Minh DucCorresponding Author Contact Information, a, E-mail The Corresponding Author and Kanit Wattanavichiena
aMechanical Engineering Department, Faculty of Engineering, Chulalongkorn University, Phaya-Thai Road, Patumwan, Bangkok 10330, Thailand
Received 22 July 2006;
accepted 29 March 2007.
Available online 21 May 2007.
– Lube oil viscosity increased with oil working time. However, after 100 h, it was in an acceptable range. This might be due to a larger amount of oil being added during the test.
– The factors having high concentration in lube oil are presented in Table 10. It is noted that not all the oil sample results are in that table. From the beginning, the chromium concentration was at an abnormal level (A); second level warning limit. This revealed that the first and fourth piston ring wear was very high. Iron concentration was at the first level warning (C) after 33.3 h and at abnormal level (A) after 144 h of the test. Aluminium concentration was at the first level warning (C) after 16 h and at abnormal level (A) after about 33 h of the test. Aluminium in the lube oil results from destruction of the piston. Fig. 39 shows the piston picture after the endurance test. Since the engine operated at higher fuel air equivalent ratio and combustion took place in the homogeneous charge, the combustion period might be shorter and combustion temperature might become too high for the piston and ring to withstand. Silicon concentration was always at the first level warning (C).
Table 10.
Oil analysis results
Engine working time (h) Lubricant oil change Note
First time Second time Third time
3.86 16.41 33.3 61.5 78.5 100.7 121.5 144 183 226.6 242.5 C A
Iron – – C C C – C A A A A >25 ppm >40 ppm
Chromium A A A A A A A A A A A >1 ppm >2 ppm
Aluminium – C A A A A A A A A A >4 ppm >6 ppm
Silicon C C C C C C C C C C C >15 ppm >25 ppm
Viscosity (100 °C) – – – – – – – – – – – <12.7 sCt >13.4 sCt
Full-size table
C: caution (first level warning limit), A: abnormal (second level warning limit).
View Within Article
Full-size image (36K) - Opens new window Full-size image (36K)
Fig. 39. Destruction of piston crown due to high thermal load.
However DIeselGas claim:
It would be interesting to know if anyone on here had done oil analysis and can support this claim or not.Engine oil analysis has proven that DieselGas significantly reduces oil contamination. It is possible to extend oil change intervals for some applications, thus saving on downtime and consumable costs. We recommend conducting engine oil analysis on each engine before extending any oil drain interval.
OldBushie
I might do it just to have a look,it's only $35.I have no interest in worrying about it,I don't worry about my motor in any way actually,I just service it and drive it,it's worked out fine so far. Pat
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interesting
Firstly it answers the question of if fumigation is done in other countries, in this case Thailand. no surprise as I have posted before that fumigation is common in Thailand, mainly in larger trucks.
2 other points of interest regarding this report firstly it states that biogas is used and not LPG. Biogas being basically methane and hydrogen with a bit of CO2 chucked in for good measure.
Secondly you are unable to get unblended diesel in Thailand, it is at best 25% bio diesel or at worse 60% coconut oil mixed with aviation kero. In some places its just pot luck as what you get.
Pom tamnarn be sarm dos sa dor, ubonratchatani, logistics, kou burn weapons karp
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if anyone is intrested Cavpower in adelaide do oil testing, $38.00 . you pick up a kit and pay first.
Wizard
correct me if I'm wrong, but at retail prices, the whole diesel gas arguement regarding "economy" ceases to be economic...
sound familiar? something akin to a certain *cough* home insulation *cough* program that is being back pedalled away from at a speed unseen in recent history...
there also seems to be a school of thought that diesel gas is something of a perpetual free energy machine - in that it creates power for "free" - it aint free, it costs you the same amount of energy as would be found in the equivalent amount of deisel. I better go install 19 hiclones, this way I'll be able to run my landy and save approximately 160% of the fuel consumed without them...
dunno why these things end up in slanging matches...
YarnMaster
I think it may have been the last budget that Peter Costello bought in, where he put an excise on LPG - as petrol and diesel had excise, so it is only fair to have excise on LPG
From memory it was to be increased over a number of years, but I can't remember which year it was to start or the other details.
Edit: Searched for some info:
LPG for cars, previously free of excise, will be taxed by 2.5 cents per litre from mid-2008. That'll go up to an eventual rate of 12.5 cents per litre by 2012.
Last edited by Bush65; 28th April 2010 at 05:19 PM. Reason: Extra info added
AT REST
People hold opinions, are loath to consider another one, therefore everyone else is wrong...
As far as economy goes, results posted on this forum and elsewhere show that direct replacement of x litres/100km of diesel with x litres /100km LPG (up to 20%) is totally realistic. As LPG has a lower heat value than diesel then something is obviously happening that but by saying this I am risking 100 snarly replies denying this. And if LPG is 1/2 the price of diesel then there's a possible 10% saving in running cost as a minimum.
And yes many people have benefitted from the insulation program, a few have died which is sad. Would they have been headline news if there hadn't been political mileage in reporting these deaths? Dunno.
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