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When starting from cold, the engine's combustion efficiency is reduced because the cold engine block draws heat out of the cylinder in the compression stroke. The result is that fuel is not combusted fully, resulting in blue and white smoke and lower power outputs until the engine has warmed. This is especially the case with indirect injection engines, which are less thermally efficient. With electronic injection, the timing and length of the injection sequence can be altered to compensate for this. Older engines with mechanical injection can have mechanical and hydraulic governor control to alter the timing, and multi-phase electrically controlled [[glow plug]]s, that stay on for a period after start-up to ensure clean combustion—the plugs are automatically switched to a lower power to prevent their burning out.
When starting from cold, the engine's combustion efficiency is reduced because the cold engine block draws heat out of the cylinder in the compression stroke. The result is that fuel is not combusted fully, resulting in blue and white smoke and lower power outputs until the engine has warmed. This is especially the case with indirect injection engines, which are less thermally efficient. With electronic injection, the timing and length of the injection sequence can be altered to compensate for this. Older engines with mechanical injection can have mechanical and hydraulic governor control to alter the timing, and multi-phase electrically controlled [[glow plug]]s, that stay on for a period after start-up to ensure clean combustion—the plugs are automatically switched to a lower power to prevent their burning out.


Particles of the size normally called PM10 (particles of 10 [[micrometre]]s or smaller) have been implicated in health problems, especially in cities. Some modern diesel engines feature [[diesel particulate filter]]s, which catch the black soot and when saturated are automatically regenerated by burning the particles. Other problems associated with the exhaust gases (nitrogen oxides, sulfur oxides) can be mitigated with further investment and equipment; some diesel cars now have catalytic converters in the exhaust.
Particles of the size normally called PM10 (particles of 10 [[micrometre]]s or smaller) have been implicated in health problems, especially in cities. Some modern diesel engines feature [[diesel particulate filter]]s, which catch the black soot and when saturated are automatically regenerated by burning the particles.

All diesel engine exhaust emissions can be significantly reduced by using [[biodiesel]] fuel. Oxides of nitrogen do increase from a vehicle using biodiesel, but they too can be reduced to levels below that of fossil fuel diesel, by changing fuel injection timing.


==Variation with engine conditions==
==Variation with engine conditions==

Revision as of 11:18, 25 March 2011

Diesel particulate matter (DPM), sometimes also called diesel exhaust particles (DEP), is the particulate component of diesel exhaust, which includes diesel soot and aerosols such as ash particulates, metallic abrasion particles, sulfates, and silicates. When released into the atmosphere, DPM can take the form of individual particles or chain aggregates, with most in the invisible sub-micrometre range of 100 nanometers, also known as ultrafine particles (UFP) or PM0.1.

Health effects

Diesel combustion exhaust is a major source of atmospheric soot and fine particles, which is a fraction of air pollution implicated in human heart and lung damage. Diesel exhaust also contains nanoparticles. Since the study of the detrimental health effects of nanoparticles (nanotoxicology) is still in its infancy, the full extent of negative health effects from nanoparticles produced by all types of diesel are unknown.

The main particulate fraction of diesel exhaust consists of fine particles. Because of their small size, inhaled particles may easily penetrate deep into the lungs. The rough surfaces of these particles makes it easy for them to bind with other toxins in the environment, thus increasing the hazards of particle inhalation. Exposures have been linked with acute short-term symptoms such as headache, dizziness, light-headedness, nausea, coughing, difficult or labored breathing, tightness of chest, and irritation of the eyes and nose and throat. Long-term exposures can lead to chronic, more serious health problems such as cardiovascular disease, cardiopulmonary disease, and lung cancer.

In 2001, the mortality within the German population (82 million people) was according to the official report 2352 of the Umweltbundesamt Berlin (Federal Environmental Agency of Germany) at least 14400 people because of Diesel soot exposure.

Since the study of the detrimental health effects of nanoparticles (nanotoxicology) is still in its infancy, the full extent of negative health effects from nanoparticles produced by all types of diesel are unknown. One study, reported in the Lancet in 2011, has already revealed that traffic exhaust is the single most serious preventable cause of heart attack in the general public, the cause of 7.4% of all attacks.[1]

The study of nanoparticles and nanotoxicology is still in its infancy, but the full health effects from nanoparticles produced by all types of diesel are unknown. It is already clear enough, however, that the health detriments of fine particle emissions are severe and pervasive. Although one study found no significant evidence that short term exposure to diesel exhaust results in adverse extra-pulmonary effects, effects that are often correlated with an increase in cardiovascular disease,[2] a 2011 study in The Lancet concluded that traffic exhaust is the single most serious preventable cause of heart attack in the general public, the cause of 7.4% of all attacks.[3]

The types and quantities of nanoparticles can vary according to operating temperatures and pressures, presence of an open flame, fundamental fuel type and fuel mixture, and even atmospheric mixtures. As such, the resulting types of nanoparticles from different engine technologies and even different fuels are not necessarily comparable. In general, the usage of biodiesel and biodiesel blends results in decreased pollution. One study has shown that the volatile component of 95% of diesel nanoparticles is unburned lubricating oil.[4] Long term effects still need to be further clarified, as well as the effects on susceptible groups of people with cardiopulmonary diseases.

Diesel engines can produce black soot (or more specifically diesel particulate matter) from their exhaust. The black smoke consists of carbon compounds that were not combusted, because of local low temperatures where the fuel is not fully atomized. These local low temperatures occur at the cylinder walls, and at the outside of large droplets of fuel. At these areas where it is relatively cold, the mixture is rich (contrary to the overall mixture which is lean). The rich mixture has less air to burn and some of the fuel turns into a carbon deposit. Modern car engines use a diesel particulate filter (DPF) to capture carbon particles and then intermittently burn them using extra fuel injected directly into the filter. This prevents carbon buildup at the expense of wasting a small quantity of fuel.

The full load limit of a diesel engine in normal service is defined by the "black smoke limit", beyond which point the fuel cannot be completely combusted. As the "black smoke limit" is still considerably lean of stoichiometric, it is possible to obtain more power by exceeding it, but the resultant inefficient combustion means that the extra power comes at the price of reduced combustion efficiency, high fuel consumption and dense clouds of smoke. This is only done in specialized applications (such as tractor pulling competitions) where these disadvantages are of little concern.

When starting from cold, the engine's combustion efficiency is reduced because the cold engine block draws heat out of the cylinder in the compression stroke. The result is that fuel is not combusted fully, resulting in blue and white smoke and lower power outputs until the engine has warmed. This is especially the case with indirect injection engines, which are less thermally efficient. With electronic injection, the timing and length of the injection sequence can be altered to compensate for this. Older engines with mechanical injection can have mechanical and hydraulic governor control to alter the timing, and multi-phase electrically controlled glow plugs, that stay on for a period after start-up to ensure clean combustion—the plugs are automatically switched to a lower power to prevent their burning out.

Particles of the size normally called PM10 (particles of 10 micrometres or smaller) have been implicated in health problems, especially in cities. Some modern diesel engines feature diesel particulate filters, which catch the black soot and when saturated are automatically regenerated by burning the particles.

Variation with engine conditions

The types and quantities of nanoparticles can vary according to operating temperatures and pressures, presence of an open flame, fundamental fuel type and fuel mixture, and even atmospheric mixtures. As such, the resulting types of nanoparticles from different engine technologies and even different fuels are not necessarily comparable. In general, the usage of biodiesel and biodiesel blends results in decreased pollution.

Effect of engine lubricating oil

One study has shown that the volatile component of 95% of diesel nanoparticles is unburned lubricating oil.[5] Long term effects still need to be further clarified, as well as the effects on susceptible groups of people with cardiopulmonary diseases.

Regulation

Although the American Mine Safety and Health Administration issued a health standard in January 2001 designed to reduce exposure in underground metal and nonmetal mines, on September 7, 2005, MSHA published a notice in the Federal Register proposing to postpone the effective date from January 2006 until January 2011.

To rapidly reduce particulate matter from heavy-duty diesel engines in California, the California Air Resources Board created the Carl Moyer Program to provide funding for upgrading engines ahead of emissions regulations.

References

  1. ^ Public health importance of triggers of myocardial infarction: comparative risk assessment
    Reference: Lancet 2011, Issue 9767; 377: 732 - 740
    Date published: Feb. 25, 2011
    "Taking into account the OR and the prevalences of exposure, the highest PAF was estimated for traffic exposure (7.4%)... "
    "… [O[dds ratios and frequencies of each trigger were used to compute population-attributable fractions (PAFs), which estimate the proportion of cases that could be avoided if a risk factor were removed. PAFs depend not only on the risk factor strength at the individual level but also on its frequency in the community. ... [T]he exposure prevalence for triggers in the relevant control time window ranged from 0.04% for cocaine use to 100% for air pollution. ... Taking into account the OR and the prevalences of exposure, the highest PAF was estimated for traffic exposure (7.4%) ...
    http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2810%2962296-9/abstract doi:10.1016/S0140-6736(10)62296-9
  2. ^ http://www.blackwellpublishing.com/isth2005/abstract.asp?id=46528 Exposure to Diesel Nanoparticles Does Not Induce Blood Hypercoagulability in an at-Risk Population (Abstract)
  3. ^ Nawrot, Perez, Künzli, Munters, Nemery Public health importance of triggers of myocardial infarction: comparative risk assessment The Lancet Volume 377, Issue 9767, Pages 732 - 740, 26 February 2011 http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2810%2962296-9/abstract doi:10.1016/S0140-6736(10)62296-9
    "Taking into account the OR and the prevalences of exposure, the highest PAF was estimated for traffic exposure (7.4%)... "
    "… [O[dds ratios and frequencies of each trigger were used to compute population-attributable fractions (PAFs), which estimate the proportion of cases that could be avoided if a risk factor were removed. PAFs depend not only on the risk factor strength at the individual level but also on its frequency in the community. ... [T]he exposure prevalence for triggers in the relevant control time window ranged from 0.04% for cocaine use to 100% for air pollution. ... Taking into account the OR and the prevalences of exposure, the highest PAF was estimated for traffic exposure (7.4%) ...
  4. ^ On-line measurements of diesel nanoparticle composition and volatility
  5. ^ http://dx.doi.org/10.1016/S1352-2310(02)01017-8 On-line measurements of diesel nanoparticle composition and volatility

Partculates: see also

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